This invention relates to electronics, and more particularly to compositions useful for producing resistor patterns adherent to substrates.
Resistor compositions which are applied to and fired on dielectric substrates (glass, glass-ceramic, and ceramic) usually comprise finely divided inorganic powders (e.g., metal and/or oxide particles and inorganic binder particles) and are commonly applied to substrates using so-called "thick film" techniques, as a dispersion of these inorganic powders in an inert liquid medium or vehicle. Upon firing or sintering of the film, the metallic and/or oxide component of the composition provides the functional (conductive) utility, while the inorganic binder (e.g., glass, crystalline oxides such as Bi.sub.2 O.sub.3, etc.) bonds the metal particles to one another and to the substrate. Thick film techniques are contrasted with thin film techniques which involve deposition of particles by evaporation or sputtering. Thick film techniques are discussed in "Handbook of Materials and Processes for Electronics," C. A. Harper, Editor, McGraw-Hill, N.Y., 1970, Chapter 12.
Numerous patents disclose the compositions of pyrochlore related oxides of the general formula A.sub.2 B.sub.2 O.sub.6-7, plus glass binder, dispersed in a vehicle, and for printing and firing to produce resistor films. Such patents include Bouchard U.S. Pat. No. 3,583,931, Hoffman U.S. Pat. No. 3,553,109 and Bouchard et al. U.S. Pat. No. 3,896,055, each of which is incorporated by reference herein.
Faber et al. U.S. Pat. No. 3,304,199 discloses resistor compositions of the rutile RuO.sub.2 plus glass, and is also incorporated by reference herein.
Casale et al. U.S. Pat. No. 3,637,530 teaches resistor compositions comprising a single phase (col. 2, line 64) reaction product of certain proportions of niobium pentoxide and ruthenium dioxide, plus glass, dispersed in a vehicle. It is disclosed that the presence of unreacted niobium pentoxide is extremely harmful (col. 2, line 66) to achieving patentee's desired results. Lead borosilicate glass is disclosed in Example 2 but no compositional limits are mentioned. The Nb.sub.2 O.sub.5 /RuO.sub.2 product of Casale et al. is formed by preheating the reactants at temperatures not less than 1000.degree. C. (col. 2, line 56).
There is a need for resistor compositions capable of producing fired resistor films which can exhibit reduced difference (spread) between hot and cold temperature coefficient of resistance (TCR), i.e., 0.+-.250 ppm/.degree. C., preferably 0.+-.100 ppm/.degree. C., and yet have a low coefficient of variation in resistivity.